This nonprovisional application claims priority under 35 U.S.C. xc2xa7119(a) on Patent Application No. 2000-358571 filed in Japan on Nov. 24, 2000, which is herein incorporated by reference.
1. Field of the Invention
The present invention relates to a pickup apparatus for separating semiconductor chips from an adhesive sheet.
2. Description of the Related Art
A production process of a semiconductor device is divided into first and second steps. In the first step, circuit components are formed on a semiconductor wafer. In the second step, the semiconductor wafer including the circuit components is diced into separate semiconductor chips, and the diced semiconductor chips are sealed in respective semiconductor packages.
In the second step, in order to convey the semiconductor chips obtained by dicing the semiconductor wafer to a packaging apparatus, a pickup apparatus picks up the semiconductor chips from an adhesive sheet used for fixing the semiconductor chips. Examples of conventional pickup apparatuses are as follows.
FIG. 4 illustrates one of the conventional pickup apparatuses. This pickup apparatus includes a pushup unit 8 provided with pushup pins 7, and an aspiration mechanism, i.e., a vacuum mechanism (not shown). Firstly, the pickup apparatus brings a back face of an adhesive sheet 2 into contact with the pushup unit 8 and causes the adhesive sheet 2 to be held on the pushup unit 8 using the aspiration mechanism. Next, the pushup pins 7 housed in the pushup unit 8 are raised so as to push up a back face of a semiconductor chip 1, whereby the semiconductor chip 1 is separated from the adhesive sheet 2. Finally, the semiconductor chip 1 is picked up using a collet 6.
Japanese Laid-Open Publication No. 2000-195877 discloses a pickup apparatus illustrated in FIGS. 5(a), (b), and (c). As illustrated in FIG. 5(a), this conventional pickup apparatus includes: a sheet holding mechanism (not shown) for holding a dicing sheet 13 (corresponding to the adhesive sheet 2 illustrated in FIG. 4) to which a semiconductor chip 11 is attached when the dicing sheet 13 is in a stretched state; a holding stage 12 in which grooves 12a connected to a plurality of aspiration paths (through holes) 12b (in FIGS. 5(a), (b) and (c), a distance between rightmost and leftmost paths corresponds to a length of the semiconductor chip 11); and an aspiration mechanism, i.e., a vacuum mechanism (not shown) for vacuum-holding the dicing sheet 13 to the holding stage 12 when separating the semiconductor chip 11 from the dicing sheet 13. In order to pick up the semiconductor chip 11 attached to the dicing sheet 13 using this conventional pickup apparatus, at first, the aspiration mechanism is operated so as to vacuum-hold the dicing sheet 13 to the holding stage 12 along the grooves 12a, so that as illustrated in FIG. 5(b), gaps are made between the semiconductor chip 11 and the dicing sheet 13, and the semiconductor chip 11 is caused to be easily separated from the dicing sheet 13. Thereafter, the semiconductor chip 11 is picked up using a collet 14 as illustrated in FIG. 5(c).
In this conventional pickup apparatus, the grooves 12a of the holding stage 12 are in the form of either concentric circles (FIG. 6 (a)), parallel lines (FIG. 6 (b)) a grille (FIG. 6 (c)) etc. The form of the grooves 12a can be suitably selected from these forms according to an external form of the semiconductor chip 11 so as to cause the semiconductor chip 11 to be easily peeled off the dicing sheet 13. In this conventional technique, since the holding stage 12 is replaced with another holding stage 12 of a suitable size according to a type of a semiconductor chip, e.g., a difference in size between different types of semiconductor chips, the grooves 12a are provided in the holding stage 12 across almost an entire surface thereof. The structures of Conventional Examples 1 and 2 have the following problems.
In the structure of Conventional Example 1 (FIG. 4), the pushup pins 7 which are sufficiently sharp so as to pierce the adhesive sheet 2 are required, and since such sharp pushup pins 7 push up the semiconductor chip 1, the back face of the semiconductor chip 1 is likely to be damaged. In particular, by supporting the semiconductor chip 1 on a few points, such as the pushup pins 7, stress is concentrated on those specific portions of the semiconductor chip 1, so that the semiconductor chip 1 may be damaged. In the case where the semiconductor chip 1 is thin, the semiconductor chip 1 can be cracked by the pushup action of the pushup pins 7.
In the structure of Conventional Example 2 (FIGS. 5(a)-(c) and 6(a)-(c)), a size of the holding stage 12 is optimized according to a size of the semiconductor chip 11 to be picked up. However, in the case where undulating grooves 12a are provided in the holding stage 12 across almost the entire surface thereof, other semiconductor chips adjacent the semiconductor chip 11 partially overlap with the holding stage 12 in areas 20 indicated by oblique lines in FIG. 7, so that not only is the semiconductor chip 11 separated from the dicing sheet 13, but also the other semiconductor chips adjacent the semiconductor chip 11 may be caused to be partially separated from the dicing sheet 13, where these other semiconductor chips should be fixed firmly to the dicing sheet 13 until they are meant to be picked up. Accordingly, it is possible for the other semiconductor chips adjacent the semiconductor chip 11 to be completely separated from the adhesive sheet 13 and scattered about when a semiconductor wafer including the semiconductor chips is moved. Since a size of an aspiration unit including the holding stage 12 cannot be small under restrictions of the pickup apparatus, in particular, when the size of the semiconductor chips is small, the other semiconductor chips adjacent the semiconductor chip 11 may be scattered about. This particularly causes a problem when the pickup apparatus is operated by automation.
According to one aspect of the present invention, there is provided a semiconductor chip pickup apparatus including an aspiration section and an aspiration unit connected to the aspiration section, in which the aspiration unit includes a stage for mounting the semiconductor chip thereon and an adhesive sheet is attached to the semiconductor chip between the stage and the semiconductor chip, the stage includes undulations in at least a part of an area in which the semiconductor chip is mounted, and by operating the aspiration section, a suction force is applied to at least a part of an area in which the undulations are formed.
According to one embodiment of the invention, the stage may be replaceable according to a type of the semiconductor chip.
According to another embodiment of the invention, at least a part of the stage including at least a part of the undulations may be formed of a porous material.
According to still another embodiment of the invention, at least one through hole may be formed in the area in which the undulations are formed.
According to still another embodiment of the invention, the pickup apparatus may further include a heating section for heating the undulations provided in the stage.
Hereinafter, functions of the semiconductor chip pickup apparatus of the present invention are described.
The semiconductor chip pickup apparatus of the present invention includes the aspiration section and the aspiration unit connected to the aspiration section. In a structure of the semiconductor chip pickup apparatus, by operating the aspiration section, a suction force is applied to at least a part of the undulations which are at least a part of an area formed in a stage of the aspiration unit in which a semiconductor chip is mounted. The aspiration section is operated so as to aspirate an adhesive sheet attached to the semiconductor chip and hold the adhesive sheet on the stage along the undulations to which a suction force is applied, and thus the adhesive sheet is partially separated from the semiconductor chip. This lowers adhesion between the semiconductor chip and the adhesive sheet, and thus the pickup of the semiconductor chip can be facilitated. Since it is not required to use conventional pushup pins, the semiconductor chip cannot be damaged by pushup pins and can be picked up in a stable condition. Moreover, since the undulations provided in the stage are formed in at least a part of the area in which the semiconductor chip is mounted, only a semiconductor chip to be picked up can be separated from the adhesion sheet and other semiconductor chips adjacent the semiconductor chip to be picked up can not be scattered about due to partial or full separation from the adhesive sheet. Even a small-sized semiconductor chip can be picked up in a stable condition from the adhesive sheet, and thus the present invention is suitable for use in an automated semiconductor chip producing apparatus or process.
Moreover, in the semiconductor chip pickup apparatus of the present invention, the stage provided to the aspiration unit is replaceable according to a type (size) of the semiconductor chip. Thus, the aspiration unit itself is not required to be adapted for a size of the semiconductor chip, such that it is preferable to use the aspiration unit which is slightly larger than the semiconductor chip. With this structure, areas in the stage in which the undulations are not formed effectively serve to fix the other semiconductor chips adjacent the semiconductor chip to be picked up. Moreover, even when the semiconductor chip pickup apparatus of the present invention is used for different types of semiconductor chips, only the stage is required to be replaced with another stage according to the sizes of the semiconductor chips, thereby eliminating complicated adjustments, which are required for replacing pushup pins, for example.
Moreover, in the semiconductor chip pickup apparatus of the present invention, at least a part of the stage including at least a part of the undulations is formed of a porous material, and thus the adhesive sheet attached to the semiconductor chip can be effectively aspirated.
Alternatively, in the semiconductor chip pickup apparatus of the present invention, at least one through hole is formed in the area in which the undulations are formed, and thus the adhesive sheet attached to the semiconductor chip can be effectively aspirated.
Moreover, the semi conductor chip pickup apparatus of the present invention further includes a heating section for heating the undulations provided in the stage, and thus by heating the aspiration unit, such that heat from the aspiration unit lowers adhesion of the adhesive sheet to the semiconductor chip, separation of the semiconductor chip from the adhesive sheet can be facilitated. In particular, an aspiration cylinder which is a main part of the aspiration unit is a suitable member to be provided with the heating section.
Thus, the invention described herein makes possible the advantage of providing an apparatus for picking up semiconductor chips which is capable of picking up only a semiconductor chip to be picked up in a semiconductor chip pickup step by lowering adhesion of an adhesive sheet so as to separate the semiconductor chip to be picked up from the adhesive sheet without causing damage to the semiconductor chips even when they are thin.
This and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.